Many code editors, such as source code editors and text editors, provide formatting of text in accordance with syntax (e.g., grammar) or semantics (e.g., meaning). For example, a code editor could render comments in italics and code in bold font. Text is classified as having a specific display characteristic or format, and each text run has associated therewith the specific classification for the text. As described herein a text run comprises a sequence of text characters each of which has the same formatting properties (for example, font family and color). Classifiers are typically bundled together such that adding or modifying a classification requires modification of existing classifiers. Thus, if a user desires to add additional classification logic to the code editor, the user must add the classification logic and recompile the code editor. This process can be burdensome, time consuming, and inefficient.